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Electrical Grid 1 > Chapter 8 > Flashcards

Chapter 8 Flashcards

Transmission

1
Q

Common comparison for Transmission Lines?

A
  • Our highway system

- As trucks deliver goods, Transmission Lines deliver power

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2
Q

How are Transmission Lines recognized?

A
  • Large, tall structures either steel or wood

- Large aluminum conductors

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3
Q

About how far apart are Transmission Line Structures?

A

1,000’

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4
Q

What is the basic function of a Transmission Line?

A

To take large amounts of bulk power from a source and transmit it over a distance to a given point where it can be used.

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5
Q

What is the main objective of a Transmission Line?

A

To deliver power with a minimum of loss.

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6
Q

What is DC?

A

Direct Current has less line losses and only takes two conductors (+,-) Can be economical for large amounts of power over long distances. But to convert from DC to AC installing the equipment to do so is VERY expensive

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7
Q

How are transmission structures chosen?

A

Based on the voltage of the line, the right of way size, geographical terrain, weather, size of conductor, and construction considerations.

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8
Q

What is one key consideration in the choice of structure?

A

Whether two circuits are required immediately or in the future

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9
Q

Common properties of Wood Pole Structures?

A
  • 345kV>
  • Construction requirements are relatively simple and components are easily assembled
  • Maintenance requirements of testing and treating the pole butts
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10
Q

Common properties of Tubular Steel Poles?

A
  • More aesthetically acceptable and have a longer life span than wooden poles, which decay
  • Construction is more complicated with steel poles that use a poured cylindrical base
  • Some are direct buried
  • More expensive
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11
Q

Common properties of the Lattice-Type Steel?

A
  • Structure built with pieces of angle steel bolted together in a lattice arrangement
  • 345kV<
  • Good strength characteristics and work well for double circuit configurations
  • Take more time to assemble due to number of parts
  • More extensive footings which take forever to construct (Separate crew for Footing Construction)
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12
Q

Common properties of insulators?

A
  • As voltage increases, size of insulator increases

- Used to be porcelain and glass insulators, now polymer

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13
Q

What are the common types of insulators?

A
  • Porcelain Suspension
  • Porcelain Line Post
  • Polymer Suspension
  • Polymer Line Post
  • Glass Suspension
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14
Q

What is a suspension insulator?

A

Insulator used to support the full line tension in a dead end configuration, or to support the span weight in a true suspension configuration.

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15
Q

Difference in mechanical ratings of insulators?

A

Dead end configuration would typically have a higher rating than one in a suspension configuration.

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16
Q

What are conductors typically made of?

A

Strands from aluminum or some form of aluminum alloy

17
Q

What is used to add strength in a conductor?

A

Some conductors are reinforced with steel

18
Q

How are sizes and types chosen for conductors?

A
  • How much power the line needs to carry
  • Length of the line
  • Span Lengths
  • Weather Environment
  • Line Losses
  • Cost of the Conductor
19
Q

What style conductor is used to deliver large amounts of power at extra high voltages over long distances?

A

Bundled Conductors

20
Q

What does the term bundled mean?

A
  • More than one conductor per phase

- Typically 2-4 conductors per phase

21
Q

What are bundled conductors used for?

A
  • Increase the capacity of a line
  • Reduce radio noise
  • Corona Loss
22
Q

What is Corona Loss?

A
  • Phenomenon occurs at high voltages, which is the result of the ionization of the air around the conductor.
  • Effects are audible and are visible at night
23
Q

What are the max size Conductors can be?

A

1-3/4” in Diameter and Weigh 2-1/2lbs per foot

24
Q

What determines the voltage level of a Transmission Line?

A
  • Length of the line
  • Amount of power to be delivered
  • Voltage of the existing system
  • Cost of Losses
25
Q

What is a Kilovolt?

A

1000 Volts

26
Q

What are the Main Grid voltages?

A

230kV, 2345kV, 500kV, and 765kV

27
Q

What are the Subtransmission Voltages?

A

44kV, 69kV, 115kV,, and 138kV

28
Q

What do higher voltages require?

A
  • Larger right of way
  • Larger Structures
  • More Insulation
29
Q

What do Transmission Lines do for Lightning Protection?

A
  • Some form of “Shielding” or “Static Wires”
  • Can be recognized by one or two smaller conductors fastened to the top structures above the phase conductors
  • These conductors are grounded and provide a path to ground from lightning surges
30
Q

What do shield wires do for communications?

A
  • Manufactured with a fiber optic cable in the center so the conductor can perform two functions
    1. ) The outer portion of the conductor will conduct the lightning surges to ground.
    2. ) The inner fiber optic conductor will provide capacity for voice and data communications
31
Q

How are transmission lines ran in large cities?

A

It’s an extremely expensive process and very time consuming but the wires are ran underground
In New York its system uses pipe-type, oil-filled cable, with three insulating cables in one pipe filled with oil for cooling purposes.

32
Q

How is Right-of-Way determined?

A

-Based on terrain, existing development etc.

33
Q

What must a company obtain to construct and maintain a line?

A

Legal Rights

34
Q

Why are Right-of-Ways difficult to obtain?

A

Objections of property owners

35
Q

What determines the size of the right-of-way?

A

Voltage of the line, type pf structure and conductor spacing

-Also EMF

36
Q

For a major transmission lines how long may it take to secure rights?

A

3-5 years

37
Q

What must a utility provide to the owner of land?

A

Reasonable Compensation

38
Q

What must a Right-of-Way be clear of?

A

trees, vegetation and anything else that could cause an outage

Electrical Grid 1 (10 decks)

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